The present invention is directed generally to liquid dispensing systems having controllably movable cartridges and more specifically to liquid dispensing systems that utilize liquid dispensing needles or transfer pins and a system and method for the self-cleaning thereof.
Several types of prior art dispensing systems are used for dispensing metered amounts of liquid or paste for a variety of applications. One such application is in the assembly of printed circuit boards and integrated circuit chips. Dispensing systems are used in this application for the process of encapsulating the integrated circuits with an encapsulate material and in the process of under filling flip integrated circuit chips with an encapsulant. Prior art dispensing systems are also used for dispensing dots or balls of liquid epoxy or solder onto circuit boards and integrated circuits. The liquid epoxy and solder is primarily used to connect components within an integrated circuit.
In a typical dispensing system, a pump and dispenser assembly is mounted to a moving assembly, such as a gantry, for moving the pump and dispenser assembly along three mutually orthogonal axes (x, y, z), by servomotors or other similar devices that are controlled by a computer system or controller. To dispense a volume of liquid on a circuit board or some other substrate at a desired location, the pump and dispenser assembly, which normally includes a nozzle coupled with a dispensing needle, is moved along the horizontal x and y axes until it is located over the desired location. The pump and dispenser assembly is then lowered along the vertical z-axis until the dispensing needle is at an appropriate height over the substrate, where it dispenses a metered volume of liquid through the needle. The pump and dispenser assembly is then raised along the z-axis, moved along the x and y axes to a next desired location and then lowered along the vertical z-axis to dispense a metered volume of liquid at the next location.
In dispensing applications such as those described above, the accuracy of the volume of liquid dispensed by the system is an important feature of the system. These dispensing systems are effective in dispensing precise amounts of metered material onto a substrate, however, over time an amount of residual or other material tends to build up on the exterior surface of the dispensing needle or pin. The build up of excess material leads to unwanted material drops, material splatter and or line/dot width variation.
It is therefore desirable to have a dispensing system that is capable of periodically cleaning residual material from the exterior surface of the dispensing needle or transfer pin.
In one aspect, the present invention is directed to a needle cleaning system for removing an amount of residual material from a liquid dispensing needle or pin. The system includes a container assembly having at least one orifice, a vacuum source operatively connected to the container assembly wherein the vacuum source creates an airflow through the at least one orifice into the container assembly and a control system that positions the liquid dispensing needle or pin relative to the at least one orifice in the container assembly wherein the residual material is removed from the dispensing needle or pin by the airflow.
The system may be constructed and arranged such that the residual material is removed from the liquid dispensing needle or pin without contact occurring between the dispensing needle or pin and the container assembly. The system may include a disposable cup for collecting an amount of removed residual material. The system may include a tube for directing the airflow towards the bottom of the disposable cup. The container assembly may include a plurality of various diameter orifices to accommodate a variety of various gauge dispensing needles or pins. The vacuum source may be coupled with one or more of the plurality of different diameter orifices whereby an airflow is created through the one or more of the plurality of different diameter orifices into the container assembly.
Another aspect of the invention is directed to a needle cleaning system for removing an amount of residual material from a liquid dispensing needle or pin where the system includes a container assembly having an iris-type shutter having a variable diameter opening, a vacuum source operatively connected to the iris-type shutter wherein the vacuum source creates an airflow through the variable diameter opening and into the container assembly and a control system that positions the liquid dispensing needle or pin relative to the iris-type shutter such that the airflow through the variable diameter opening causes the removal of the residual material from the dispensing needle or pin.
The system may be constructed and arranged such that the diameter of the variable diameter opening of the iris-type shutter may be increased or decreased to accommodate a variety of different gauge dispensing needles or pins. The control system may be constructed and arranged to operatively control the diameter of the variable diameter opening of the iris-type shutter. The container assembly may further include a disposable cup for collecting an amount of removed residual material.
Another aspect of the invention is directed to a self-cleaning liquid dispensing system. The system includes means for receiving a liquid from a liquid source, means for dispensing the liquid through a needle or pin onto a medium and means for removing an amount of residual material from an exterior portion of the needle or pin without contacting the needle or pin.
The system may be constructed and arranged such that the means for removing residual material includes a needle cleaning system that includes a container assembly having at least one orifice, a vacuum source operatively connected to the container assembly wherein the vacuum source creates an airflow through at least one orifice into the container assembly and means for operatively positioning the liquid dispensing needle or pin relative to the at least one orifice wherein the residual material is removed from the dispensing needle or pin without contact between the dispensing needle or pin and the orifice. The system may be constructed and arranged such that the means for operatively positioning the liquid dispensing needle or pin relative to the orifice includes a computer control system.
Another aspect of the invention is directed to a self-cleaning liquid dispensing system. The system includes at least one dispensing needle or pin, a needle cleaning system that includes at least one vacuum source for operatively removing residual material from the at least one dispensing needle or pin and means for operatively positioning one or more dispensing needles or pins relative to a vacuum source. The system may be constructed and arranged such that the needle cleaning system may include at least one container assembly. The container assembly may be constructed and arranged to include at least one orifice for receiving an end of a dispensing needle or pin. The container assembly may be constructed and arranged to include a plurality of various diameter orifices. The container assembly may be constructed and arranged to include at least one adjustable diameter orifice. The system may be constructed and arranged to include at least one vacuum source that may be coupled with the container assembly such that the vacuum source causes a stream of air to flow through an orifice and into the container assembly.
Another aspect of the invention is directed to a method for cleaning residual material from a dispensing needle or pin in a liquid dispensing system. The method includes steps of supplying at least one container assembly having at least one orifice, positioning the needle or pin relative to the at least one orifice and supplying a vacuum source for creating an airflow through the orifice and into the container assembly wherein the airflow causes residual material to be pulled from the dispensing needle or pin. The method may further include the step of removing the residual material from the dispensing needle or pin without having contact between the dispensing needle or pin and the orifice.